Derivative of a polynomial function

A polynomial is a sum of terms, and each term is a constant times a power of a variable. For example, $x^2 - 2x + 3$ is a polynomial. A polynomial in one variable is called a univariate polynomial, and it is usually written like this.

$f(x) = a_n x^n + a_{n-1} x^{n-1} + \cdots + a_2 x^2 + a_1 x + a_0$

You are given a univariate polynomial of degree at most 1. Write a program that prints the result of differentiating it.

The first line contains a univariate polynomial of degree at most 1. It has at most 2 terms, the variable is always $x$, and the terms are not separated by spaces. Each coefficient and the constant term are integers whose absolute value does not exceed 10,000. A coefficient whose absolute value is 1 is omitted. A given degree appears only once, and the terms are given from the highest degree to the lowest.

Print the result of differentiating the given polynomial on the first line. The derivative of a polynomial of degree at most 1 is a constant, so print that value as a single integer.

Use the power rule $(x^n)' = n x^{n-1}$. For two differentiable functions the sum rule $(f(x) + g(x))' = f'(x) + g'(x)$ holds.